Аннотация:Methyl viologen (MV(2+))(Cl-)2 is reduced by cesium anthracene to form neutral MV(0) whose interaction with C60 produces(MV.+)2(C60(-))2. 2.5C6H4Cl2. 0.5C6H6 (1). X-ray diffraction analysis
shows that C60(.-) radical anions form singly-bonded (C60(-))2 dimers at 100 K and are arranged in zig-zag layers. According to EPR, the
dimers dissociate in the 235–375 K range. Salt 1 contains two paramagnetic MV(.+) and C60(.-) species in the monomeric phase with strong exchange interaction. This interaction is switched off at the dimerization of C60(.-) and magnetically isolated MV(.+) pairs are formed. Spins of MV(.+) are strongly antiferromagnetically coupled
in the pairs with the Weiss temperature of 32 K and J/kB = -20 K. MV(.+) shows narrow EPR signal with g = 2.0039 and the linewidth of about 0.2 mT (T = 100 K). A plot of natural logarithm of the
dimerization constant vs. reverse temperature (at 235–375 K) allows the estimation of the energy of single C–C bonds in the (C60(-))2 dimers as 38.2 +- 0.8 kJ mol.